The vinyl laminating market comprises three major segments, namely the mobile home, furniture and paneling markets. The industry requirements for a high performance vinyl laminating adhesive are based on many requirements, but three primary standards are the following:
cross-hatch shrinkage--maximum movement of 0.0254 mm at 93.degree. C. PA1 lap sheer--no vinyl creep with a 1.8 kg weight at 71.degree.-93.degree. C. PA1 peel adhesion--3 to 7 pli (0.53 to 1.23.times.10.sup.-3 N/m). PA1 (a) 50-95 wt % aqueous polyvinyl alcohol (PVOH)-stabilized vinyl acetate/ethylene (VAE) copolymer emulsion; and PA1 (b) 5-50 wt % aqueous polyurethane-acrylic (UA) polymer dispersion, the wt %'s based on polymer solids.
Current technology used in the industry comprises two-part epoxy systems and isocyanate crosslinked VAE copolymer emulsions. Industry trends indicate attempts to move away from two-part epoxy systems due to their poor wet tack during application, long cure time, high cost and health issues. The VAE copolymer emulsion technology as been unable to achieve the high temperature requirements of the cross-hatch shrinkage and lap sheer tests. The addition of 5 pph aromatic isocyanate to a VAE copolymer emulsion has made headway into the market with improvements in heat resistance. However, this system has not be able to consistently meet the performance requirements of the cross-hatch shrinkage and lap sheer tests or duplicate the performance of the epoxy.
U.S. Pat. No. 4,921,898 discloses a VAE copolymer emulsion which is about 65-75% solids and has a viscosity of less than about 3,500 cps. The emulsion is prepared by copolymerization of vinyl acetate and ethylene monomers in the presence of a stabilizing system, consisting essentially of 2-4 wt % PVOH having a 100-600 degree of polymerization and 2-4 wt % of a surfactant.
U.S. Pat. No. 5,092,953 discloses a water-based adhesive composition comprising a PVOH stabilized vinyl chloride-ethylene copolymer latex and 5-50 wt %, based on copolymer, of a polyisocyanate material. The adhesive composition has improved pot life and is used to prepare wood composites demonstrating improved water resistance.
U.S. Pat. No. 5,173,526 discloses a method for making an aqueous polyurethane-vinyl polymer dispersion.